1. Field of the Invention
The present invention relates to a microscope in which observation methods are switchable, and specifically to a microscope in which observation methods are switchable between a relief contrast (RC) observation method and a differential interference contrast observation method or polarization observation method.
2. Description of the Related Art
Conventionally, a microscope in which observation methods are switchable in one microscope has been proposed and implemented.
Here, a conventional microscope in which observation methods are switchable will be described with reference to FIGS. 32 to 37. FIG. 32 is a schematic side view showing an overall configuration example of a conventional microscope, FIG. 33 is a schematic side view showing the extracted and enlarged condenser lens part in FIG. 32, FIG. 34 is a plan view of the RC slit part in FIG. 33 seen from the direction of the arrow X, FIG. 35 is a plan view of the slider part in FIG. 33, FIG. 36 is a plan view of the modulator shown in FIG. 32, and FIG. 37 is a plan view of the modulator shown in a positional relationship with the RC slit.
The relief contrast (RC) refers to a kind of observation methods generally called “Hoffman modulation contrast” invented by Robert Hoffman in a microscope system for phase object observation shown in Japanese Patent Application Laid-open (JP-A) No. H51-29149, for example. In addition, several kinds of observation methods based on the Hoffman modulation contrast have been invented. Further, regarding the name of the observation method, the method may be referred to as modulation contrast, IMC, LMC, RC, barrel contrast other than Hoffman modulation contrast and relief contrast. In this specification, the method is appropriately referred to as “RC observation”, which is an abbreviation of relief contrast observation.
First, in the schematic side view showing an overall configuration example of a microscope 100 in FIG. 32, basic configurations of an illumination system and an observation system will be described. The illumination light output from a light source 2 illuminates a specimen 1 via an illumination system lens 3, a mirror 4, and a condenser lens 5 provided in an illumination light axis L1. The specimen 1 illuminated by the illumination light is reflected by a mirror 9 in the middle of an observation light axis L2 and projected onto a primary image surface 10 by an objective lens 6a and an imaging lens 8 on the observation light axis L2. Then, the primary image is relayed by a relay lens 11 to form a secondary image for allowing visual observation by an ocular lens 12.
At switching to an objective lens according to magnifying power and an observation method, a revolver 7 is revolved around the observation light axis L2 and a desired lens 6a is inserted into the observation light axis L2, and a focusing handle 16 is rotationally operated. Thereby, the specimen 1 is brought into focus by vertically moving a vertical movement guide 15 that holds the revolver 7 relative to a microscope main body 17 (hereinafter, sometimes referred to as an illumination optical system housing 17) for observation. Further, when an observation is desired not visually but using an image pickup device such as a CCD, an observation by electronic imaging can be made by deflecting an optical path in a direction perpendicular to the paper surface (in a direction from the front surface to the rear surface) with a prism 13 for imaging on the image pickup device such as a CCD.
Next, the condenser lens 5 will be described in detail with reference to FIGS. 33 to 35. The condenser lens 5 has a turret 24 provided near its entrance pupil location and rotating about a rotational axis 25. To the turret 24, optical devices such as a difference interference prism (hereinafter, referred to “DIC prism”) 20 and an RC slit 21 for RC observation are detachably fixed. By rotating the turret 24, the optical devices can be insertably and removably positioned relative to the position on the illumination light axis L1 by a positioning mechanism such as a click mechanism (not shown). Further, in the turret 24, a lens 19 is fixedly provided in the illumination light axis L1.
The turret 24 has a centering mechanism with respect to the rotation of the RC slit 21 and the light axis in the part to which the RC slit 21 is attached as shown in FIG. 34. That is, the RC slit 21 is configured so that it may be urged to receive pressing force toward the center by a leaf spring 27 and the pressing force may be received by two screws 28 separately provided at the opposite side thereto. Thereby, the RC slit 21 can be centered with respect to the light axis through adjustment of the position of the RC slit 21 by turning the screws 28. Further, grooves 30 are provided on the periphery of the RC slit 21, and the RC slit 21 can be rotated in the horizontal plane by inserting an end of a knob 29 into one of the grooves 30 and moving the knob 29 in directions shown by an arrow in FIG. 34.
Furthermore, a slider 26 with two types of polarizing plates 22, 23 mounted thereon is provided above the turret 24. The slider 26 is slidably provided in right and left directions indicated by an arrow, and one of the two types of polarizing plates 22, 23 can be insertably and removably positioned on the illumination light axis L1 by moving the slider 26 in the arrow directions. The positioning mechanism is not particularly shown, but a general mechanism such as a click mechanism and stopper may be used. The polarizing plate 22 is a polarizer for RC observation (polarizing plate for RC observation) and the polarizing plate 23 is a polarizer for DIC observation (a polarizing plate for DIC observation). The polarizing plates 22, 23 can individually be rotated by operating peripheral parts 22a, 23a protruded to the outside, respectively, as shown in FIG. 35.
Subsequently, returning to FIG. 32, the observation system will be described. A slider 33 with a DIC prism 31 and a polarizing plate 32 overlapped in the light axis direction is provided below the revolver 7. The DIC prism 31 and the polarizing plate 32 can be insertably and removably positioned on the observation light axis L2 at the same time by moving the slider 33 in horizontal directions indicated by an arrow. The positioning mechanism is not particularly shown, but a general positioning mechanism such as a click mechanism and stopper may be used. Here, the polarizing plate 32 is an analyzer for DIC observation necessary for DIC observation. Further, the DIC prism 31 is not particularly shown, but is microscopically movable in the direction perpendicular to the light axis (horizontal direction) for contrast adjustment at DIC observation.
In such a configuration, first, the case of making DIC observation will be described. First, the revolver 7 is rotationally operated and the objective lens 6a for DIC is set on the observation light axis L2 as shown in FIG. 32. Then, before observation, adjustment is made following the procedure of (1) to (5) because it is necessary to adjust the polarizing plates in advance.
(1) rotationally operate the turret 24 in the condenser lens 5 for positioning a hole (not shown) on the illumination light axis L1 so that there is no optical device on the illumination light axis L1;
(2) slidingly operate the slider 26 in the condenser lens 5 so that the polarizer for DIC observation 23 is on the illumination light axis L1 as shown in FIG. 33;
(3) slidingly operate the slider 33 below the revolver 7 so that the prism for DIC 31 and the analyzer for DIC observation 32 are on the observation light axis L2;
(4) detach the ocular lens 12; and
(5) rotationally operate the polarizer for DIC observation 23 to make a crossed Nicol condition that the vibration direction is perpendicular to the vibration direction of the analyzer for DIC observation 32. In this regard, when the exit pupil of the observation optical system is seen with the ocular lens 12 detached, diagonal lines are seen, and the crossed Nicol condition occurs when the lines are the darkest. Since the vibration direction of the analyzer for DIC observation 32 is fixed to a previously set direction, the vibration direction of the polarizer for DIC observation 23 becomes the direction indicated by an arrow 23b in FIG. 5 after the adjustment.
The above (1) to (5) are the prior crossed Nicol adjustment procedure. Regarding the crossed Nicol adjustment, if the adjustment operation is once performed, readjustment is unnecessary unless misadjustment occurs.
Then, the ocular lens 12 is attached, the IDC prism 20 adapted to the type of the objective lens 6a is inserted into the illumination light axis L1, the focus is brought on the specimen 1 as described above, and thereby, DIC observation visually or with the image pickup device such as a CCD can be made.
Next, the case of making RC observation will be described. Note that the sit adjustment before observation is also necessary in the RC observation, and here, the outline of the slit adjustment will be first described. In the RC slit 21 shown in FIG. 34, a through-hole slit 21a and a polarization slit 21b are provided side by side on a thin plate made of a material that does not transmit illumination light. The through-hole slit 21a has a rectangular strip shape that transmits 100% of light. The polarization slit 21b has a rectangular strip shape to which a polarizing plate as an analyzer for RC observation (polarizing plate for RC observation) is attached. On the other hand, the modulator 18 having a circular disc shape provided on the exit pupil location within the RC objective lens 6b necessary for RC observation in the revolver 7 is formed into three areas of areas 18a, 18b, and 18c as shown in FIG. 36. The area 18a is an area completely shielded from light, the area 18b is an area formed to have transmittance of about 25%, and the area 18c is an area with transmittance of 100%. Further, it is necessary that, by the lens 19 in the condenser lens 5 and the RC objective lens 6b, the through-hole slit 21a with transmittance of 100% be projected onto the area 18b formed to have transmittance of about 25% of the modulator 18 and the polarization slit 21b be projected onto the area 18c with transmittance of 100% without running over the areas, respectively. FIG. 37 shows the states of slit images 21a′, 21b′ projected onto the modulator 18 with broken lines.
In this manner, regarding the RC slit 21 and the modulator 18, relative adjustment in the two-dimensional direction perpendicular within the surface vertical to the light axis and the rotational direction around the light axis is necessary. Specifically, the adjustment is made following the procedure of (1) to (5).
(1) under the condition that the DIC objective lens 6a shown in FIG. 32 is on the observation light axis L2, rotationally operate the revolver 7 to insert the RC objective lens 6b into the illumination light axis L1;
(2) rotationally operate the turret 24 in the condenser lens 5 to insert the RC slit 21 into the illumination light axis L1;
(3) slidingly operate the slider 26 in the condenser lens 5 to insert the polarizer for RC observation 22 into the illumination light axis L1;
(4) perform centering of the RC slit 21 and rotational adjustment to project the through-hole slit 21a and the polarization slit 21b onto the areas 18b, 18c of the modulator 18 without running over the areas, respectively; and
(5) adjust the contrast of the specimen 1 to be optimal by rotating the polarizer for RC observation 22 to change the transmittance of the polarization slit 21b of the RC slit 21.
Through the above (1) to (5), the prior adjustment operation before RC observation is finished. By operating the slider 33 to remove the DIC prism 31 and the analyzer for DIC observation 32 below the revolver 7 from the observation light axis L2, RC observation visually or with the image pickup device such as a CCD can be made.
Note that, since the size of the RC slit 21 varies according to types of the objective lens 6b in magnifying power, numeric aperture NA, or the like, the adjustment of (1) to (5) is necessary with respect to each type of the objective lens 6b and the RC slit 21 to be combined. Here, only one type of the objective lens 6b and the RC slit 21 are shown, but different types of objective lenses 6b and the RC slits 21 can be attached to the revolver 7 and the turret 24, and they are appropriately switched for use.
The combination of the respective objective lenses 6b and the RC slits 21 is 1:1, and thus, it is not necessary to readjust the procedure (1) to (4) after once adjusted unless misadjustment occurs due to an impact or the like. On the other hand, the adjustment of the polarizer for RC observation 22 shown in the step of (5) needs readjustment each time when the objective lens 6b is switched. This is because the objective lens 6b is screwed and fastened in the revolver 7. Thereby, not only in the case where the threaded position is not specified but also in the case where it is specified, the rotational direction of the built-in modulator 18 varies at about 5°, and the vibration direction of the analyzer of the modulator 18 also varies. Therefore, when the objective lens 6b is switched, the polarizer for RC observation 22 also needs readjustment according to the vibration direction of the analyzer of the modulator 18.
In JP-A-2003-050353, as the configuration of the condenser lens 5 is shown in FIG. 38, for example, the polarizer for DIC observation 23 and the polarizer for RC observation 22 are integrally provided on the DIC prism 20 and the RC slit 21 as optical devices to be combined, respectively. Through switching by the rotation of the turret 24, the polarizers and the optical devices in pairs can be inserted and removed into and from the illumination light axis L1 at the same time.